Calculating Like Columbus

Here's your nightly math! Just 5 quick minutes of number fun for kids and parents at home. Read a cool fun fact, followed by math riddles at different levels so everyone can jump in. Your kids will love you for it.

Calculating Like Columbus

It’s Columbus Day, when America celebrates Christopher Columbus’ famous 1492 trip across the Atlantic Ocean and discovery of America. Actually, he was looking for what they called the East Indies back then: all the southeast Asian countries including India, Pakistan, Nepal, Indonesia, Thailand, and so on. Columbus realized that if the world really was round, and he sailed west instead of going east all around Africa, he could reach the East Indies faster — not knowing there was a giant chunk of land blocking the way. In fact, Columbus did the math wrong and thought the Earth was about 17,000 miles around, when it’s actually 25,000. And thanks to other errors he thought Japan (“Cippangu” on the old, wrong map shown here) would be only 3,000 miles from Spain, when it’s actually 12,000 miles with a continent in between! That said, all of us in America are glad he made the mistake, and here we are.

Wee ones: Columbus took 4 total trips to America. Can you count them off from 1 to 4?

Little kids: Columbus made his second trip just 1 year after his 1492 trip. What year was the second trip? Bonus: If Columbus thought Japan was only 3,000 miles away instead of 12,000, by how many miles was he off? (Hint: You can add “thousands” the same way you can add apples or cookies.)

Big kids: If Columbus thought the world was 17,000 miles around instead of 25,000, by how many miles was he off? Bonus: If he’d tried to sail around the world 3 times, how much longer wouldthat trip have been than what he planned?

The sky’s the limit: Other explorers made brave trips, too, like Samuel de Champlain, who founded Quebec City and New France (Canada), and Ferdinand Magellan, who was the first to sail around the world. If Champlain’s big year and Magellan’s big year add to 3127 and are 89 years apart, in what year did each of them make his big discovery? (Magellan is the earlier one.)

Answers:Wee ones: 1, 2, 3, 4.

Little kids: In 1493. Bonus: 9,000 miles.

Big kids: 8,000 miles. Bonus: By 24,000 miles, 3 times the gap in his first guess (though if you multiplied it out you’d get 75,000 minus 51,000).

The sky’s the limit: In 1519 for Magellan, and 1608 for Champlain. Using algebra, we have
c + m = 3127
c – m = 89, so m = c – 89
Substituting, we get
c + (c – 89) = 3127
Add 89 to both sides to get
2c = 3216
c = 1608 and therefore m is 89 less giving us m = 1519.

About the Author

Laura Bilodeau Overdeck is founder and president of Bedtime Math Foundation. Her goal is to make math as playful for kids as it was for her when she was a child. Her mom had Laura baking while still in diapers, and her dad had her using power tools at a very unsafe age, measuring lengths, widths and angles in the process. Armed with this early love of numbers, Laura went on to get a BA in astrophysics from Princeton University, and an MBA from the Wharton School of Business; she continues to star-gaze today. Laura’s other interests include her three lively children, chocolate, extreme vehicles, and Lego Mindstorms.